Figure 9.

The hPop1 protein subunit of human RNase P and RNase MRP is present in NDF in HeLa cells during mitosis. (A and D) Labeling of interphase cell with anti-hPop1 and the S4 autoimmune antifibrillarin serum. The hPop1 protein was predominantly localized in nucleoli with weak nucleoplasmic staining whereas fibrillarin was present in the nucleolar DFC and in a coiled body (D, long arrow). (B and E) In early prophase the hPop1 protein (B) and fibrillarin (E) disperse from disintegrating nucleolar bodies. (C and F) In metaphase the hPop1 protein is found highly concentrated at the external central portion of chromosome periphery (C), whereas fibrillarin is concentrated in the entire perichromosomal region of the metaphase plate (F). (G and J) In late anaphase the hPop1 protein was seen associated with chromatids (G) where it colocalizes with fibrillarin (J), but hPop1 was also seen inside of mitotic spindle (G). (H and K) In late telophase when the nuclear envelope is formed, hPop1 protein is concentrated in the postmitotic nuclei but it is not detectable in newly reformed nucleoli (H, arrowheads) where fibrillarin is prominantly localized (K, arrowheads). In addition, both proteins colocalized in NDF in the cytoplasm (H, K, small arrows). (I and L) In late telophase/early G1 phase the hPop1 protein reenters nucleoli (I) and is colocalized with fibrillarin (L). Bar, 10 μm.